Process for manufacture of a high active detergent composition containing succinic acid

ABSTRACT

A process for making a concentrated liquid detergent composition comprising the steps of: i) mixing succinic anhydride, water and an alkaline catalyst, wherein the ratio of succinic anhydride to water is at least 4:1; ii) allowing an exothermic hydrolysis reaction to take place in a buffer tank, and iii) mixing the resulting highly active, partly neutralised succinic acid with other detergent ingredients.

BACKGROUND

Succinic acid and its salts are known ingredients of detergentcompositions. They are used for their surface active and hydrotropicproperties as well as calcium and magnesium binding capacity.

They are easily processed directly into a detergent liquid or slurry byin situ hydrolysis of the corresponding succinic anhydride, andsubsequent neutralisation.

This hydrolysis typically requires a considerable excess of water andthe presence of solvents (eg. lower alcohols), in an alkalineenvironment in order to make the hydrolysis reaction move rapidly tocompletion.

There is now a trend to more concentrated detergents containing verylittle water. As the water level is decreased in the hydrolysis step therate of reaction decreases and undesirable side reactions between theanhydride and the solvents forming, for example esters, start to becomesignificant.

Various prior art has dealt with detergent compositions containingsuccinic acid. These applications are in general, dilute.

GB-A-2 049 723, published Dec. 31, 1980, discloses a compositioncontaining partly neutralised succinic acid with one of its salts suchthat the pH is in the range from 5.5 to 8.0. It describes liquidcompositions containing 3%-50% by weight of the partly neutralisedsuccinic acid.

EP 0 028 850, published May 5, 1981, discloses a .liquid detergentcomposition containing succinates and a low level of alkyl benzenesulphonate, for improved storage stability. The application mentions theneutralisation of the acid or anhydride in situ, but there is no mentionof high active compositions.

GB 1 285 582, published Aug. 16, 1972, discloses a compositionsubstantially containing 25-90% succinic acid, which may be derived fromthe anhydride, and 10-75% nonionic surfactant. There is no disclosure ofa suitable process for making such compositions.

However, none of the prior art deals with the problem of making a highlyconcentrated solution of succinic acid which is suitable for furtherprocessing into a concentrated liquid detergent. There is a need for aprocess of hydrolysis of succinic anhydrides which can be carried outeffectively in an environment in which very little water is present.

The present invention provides a new process for hydrolysis of thesuccinic anhydride to yield a solution of at least 85% by weight ofpartly neutralised succinic acid. The process can be carried out insitu, continuously or batch-wise, and offers a flexible process formaking a concentrated liquid detergent.

SUMMARY OF THE INVENTION

A process for making a concentrated liquid detergent composition whichcomprises

(A) succinic acid ##STR1## where R is a C₁₀ -C₂₀ aklyl or C₁₀ -C₂₀alkenyl moiety; X and Y are each independently H, Na, K, oralkanolamine,

and (B) water,

characterised in that succinic anhydride, water and an alkaline catalystare:

i) mixed in a ratio of succinic anhydride to water (B) of not less than4:1 by weight in order to start an exothermic hydrolysis reaction

ii) held in a buffer tank, and

iii) mixed with other detergent ingredients.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for the hydrolysis of succinicanhydride to succinic acid in the presence of a small excess of water.The process takes place in the presence of an alkali which catalyses thereaction and partly neutralises the succinic acid. Firstly the succinicanhydride, water and alkali are intimately mixed, either by passingthrough static mixers, or, preferably, in a high shear mixer. Themixture is then stored in a buffer tank (which may be in-line in acontinuous process) until the exothermic hydrolysis reaction issubstantially completed. The resulting high active partly neutralisedsuccinic acid may then be stored or transferred directly into a batchtank or continuous process for further processing to a concentratedliquid detergent.

THE SUCCINIC ANHYDRIDE

Any succinic anhydride of the general formula: ##STR2## is suitable foruse in the present invention. The choice of R will be made by thedetergent formulator.

A particularly preferred chain is when:

R is CH₃ --(CH₂)_(n) --CH═CH--CH₂ and n=8-10 or mixtures thereof.

THE ALKALI

Any suitable alkali may be used including sodium hydroxide, potassiumhydroxide, monoethanolamine and ammonia. Preferred are sodium hydroxideand potassium hydroxide. The molar ratio of hydroxide present: hydroxideneeded for stoichiometric neutralisation, should be 0.15 or less.

The alkali may be added to the succinic acid in the form of a solution(typically 50% aqueous solution of either sodium or potassiumhydroxide). Extra water may also be added in order to ensure completehydrolysis by the following reaction: ##STR3##

However total water which is present (both added and with the aqueousalkali) should be limited in order to avoid diluting the finalcomposition, and to avoid an excessively long reaction time. It has beenfound that the ratio of succinic anhydride to water should be not lessthan 4:1 by weight.

THE HYDROLYSIS PROCESS

The reactants are brought together and mixed, preferably in a high shearmixer. Suitable mixers include Pentax (trade name), supplied by Bran andLuebbe, Germany; Dispax (trade name), supplied by Janke and Kunkel, andmixers supplied by Karg and Fryma. This mixture is then pumped intobuffer tank where the hydrolysis reaction will proceed. Preferably thebuffer tank already contains an amount of succinic acid which itselfpromotes rapid hydrolysis of the mixture. In a most preferredembodiment, the buffer tank is in-line in a continuous process and givesa residence time sufficient for hydrolysis to be substantiallycompleted. In this embodiment of the invention the buffer tank containsat all times a mixture of succinic acid, water, alkali and partlyneutralised succinic anhydride. The hydrolysis reaction is exothermic,and the temperature rises, preferably to about 90° C. The buffer tankshould be gently stirred or agitated in order to keep the reactantsmixed. In the case of a continuous process the buffer tank should bedesigned to give a residence time of from 2 to 30 minutes, preferablyfrom 5 to 20 minutes.

The high active succinic acid made according to the above ratios andprocess has a pH of less than 5.5, preferably about pH4.5 when it isdiluted to a 0.5% aqueous solution. Furthermore, after hydrolysis theratio of partly neutralised succinic acid to water will not be less thanabout 6:1 by weight.

START-UP AND SHUT-DOWN PROCEDURE

When a continuous process is in use as described hereinabove, theprocess is shut-down by firstly closing the supply of water and alkalito the mixer. The supply of succinic anhydride is allowed to continueuntil all water and alkali have been flushed through the mixer then thissupply is also shut-down. This procedure ensures that no hydrolysiscontinues in the mixer whilst not in use. Preferably not all of thesuccinic acid is flushed through the buffer tank. This means that whenthe supplies of succinic anhydride, water and alkali are switched on forstart-up, there is still some acid in the buffer tank to "seed" thehydrolysis reaction. During the period that the process is notoperating, the buffer tank should be maintained at an elevatedtemperature (typically 60°-80° C.) in order to prevent solidification ofthe succinic acid/anhydride mix.

FURTHER PROCESSING

The highly active, partly neutralised succinic acid made by the presentinvention may subsequently be added to other detergent ingredientsincluding surfactants, builders, chelants, enzymes and softening clays,in order to make a finished liquid detergent composition. An example ofthis is given hereinbelow. Preferably the high active succinic acid ismixed with compatible detergent ingredients which allow its temperatureto be reduced below 60° C., before it is mixed with lower alcohols. Suchshort chain alcohols may be present in the final formulation assolvents, examples include ethanol, propanol, propane diol and glycerol.If the succinic acid and such solvents are present at temperatures inexcess of 60° C., then undesirable side products such as esters may beformed. An intermediate composition may be formed which is a stable,pumpable liquid at temperatures below 60° C. This intermediatecomposition preferably consists of at least 40% by weight of partlyneutralised succinic acid.

EXAMPLE 1

    ______________________________________                                        Dodecyl/tetradecyl succinic anhydride                                                               300 kg/hour                                             Potassium hydroxide (50% aq. soln.)                                                                 20 kg/hour                                              Water                 40 kg/hour                                              ______________________________________                                    

Succinic anhydride, potassium hydroxide solution and water are suppliedat ambient temperature from metering pumps at the rates described above,into a Pentax KMF8 (Trade Mark) high shear mixer.

This mixture is transferred directly from the outlet port of this mixerinto the bottom of a buffer tank. The buffer tank has a diameter ofabout 0.4 m and a height of about 0.8 m, giving a residence time ofabout 17 minutes. The temperature in the buffer tank rises to 92° C. asthe exothermic hydrolysis reaction takes place.

The reacted material leaving from the top of the buffer tank has acomposition of:

    ______________________________________                                        Dodecyl/tetradecyl succinic acid (partly neutralised)                                                   90%                                                 Water                     10%                                                 ______________________________________                                    

and, when diluted to give an aqueous solution of 0.5% by weight, has apH of 4.5.

In this example, the high active, partly neutralised succinic acid ismixed with a nonionic surfactant in the ratio of 1:1. The surfactant issupplied at ambient temperature and the resulting mix has a temperatureof 55° C. The resulting mixture is a stable, pumpable intermediatecomposition at this temperature.

A finished composition is made by mixing the acid/surfactant mixturewith other detergent ingredients as follows (all given as % by weight):

    ______________________________________                                        Succinic acid/nonionic surfactant                                                                   18                                                      Ethanol & 1,2 propane diol                                                                          12                                                      Sodium hydroxide       9*                                                     Alkyl benzene sulphonic acid                                                                        12                                                      Sodium alkyl sulphate  2                                                      Citric acid            7                                                      Enzymes and minors     1                                                      Miscellaneous (suds suppressor, perfume etc.)                                                        1                                                      Water                 to balance to 100%                                      ______________________________________                                         *Level of sodium hydroxide may be varied in order to give finished pH8   

What is claimed is:
 1. A process for making a concentrated liquiddetergent composition comprising the steps:(i) forming a succinic acidhaving the formula ##STR4## wherein R is a C₁₀ -C₂₀ alkyl moiety or aC₁₀ -C₂₀ alkenyl moiety, and X and Y are each independently selectedfrom the group consisting of H, Na, K and alkanolamine, by a singleexothermic hydrolysis reaction; and (ii) mixing the succinic acid withadditional ingredients to form said concentrated liquid detergentcomposition;wherein the single exothermic hydrolysis reaction comprises(a) mixing succinic anhydride of the formula ##STR5## and water in aweight ratio of not less than 4:1 and in the presence of an alkalinecatalyst; and (b) holding the mixture in a buffer tank wherein a productcontaining the succinic acid is formed via an exothermic hydrolysisreaction.
 2. A process according to claim 1, wherein the process iscontinuous and the reactants have a residence time of at least 5 minutesin the buffer tank.
 3. A process according to claim 1, wherein thealkaline catalyst is sodium hydroxide or potassium hydroxide and presentin a molar ratio of:hydroxide present: hydroxide needed forstoichiometric neutralization of the succinic acid (a) of 0.15 or less.4. A process according to claim 3, wherein R is CH₃ --(CH₂)_(n)--CH═CH--CH₂ --and n=8-10 or mixtures thereof.
 5. A process according toclaim 2, wherein R is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --and n=8-10 ormixtures thereof.
 6. A process according to claim 1, wherein saidproduct, when diluted to give an aqueous solution of 0.5% by weight, hasa pH of less than 5.5.
 7. A process according to claim 6, wherein theprocess is continuous and the reactants have a residence time of atleast 5 minutes in the buffer tank.
 8. A process according to claim 7,wherein R is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --and n=8-10 or mixturesthereof.
 9. A process according to claim 7, wherein the alkalinecatalyst is sodium hydroxide or potassium hydroxide and present in amolar ratio of:hydroxide present: hydroxide needed for stoichiometricneutralization of the succinic acid (a) of 0.15 or less.
 10. A processaccording to claim 9 wherein R is CH₃ --(CH₂)_(n) 13 CH═CH--CH₂ --andn=8-10 or mixtures thereof.
 11. A process according to claim 7, whereinR is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --and n═8-10 or mixtures thereof. 12.A process according to claim 6, wherein the alkaline catalyst is sodiumhydroxide or potassium hydroxide and present in a molar ratioof:hydroxide present: hydroxide needed for stoichiometric neutralizationof the succinic acid (a) of 0.15 or less.
 13. A process according toclaim 12, wherein R is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --and n=8-10 ormixtures thereof.
 14. A process according to claim 6, wherein saidproduct when diluted to give an aqueous solution Of 0.5% by weight, hasa pH of about 4.5.
 15. A process according to claim 6, wherein saidproduct of step (ii) contains at least 85% by weight of the succinicacid (a).
 16. A process according to claim 1, wherein the alkalinecatalyst is sodium hydroxide or potassium hydroxide and present in amolar ratio of:hydroxide present: hydroxide needed for stoichiometricneutralization of the succinic acid (a) of 0.15 or less.
 17. A processaccording to claim 16, wherein R is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --andn=8-10 or mixtures thereof.
 18. A process according to claim 1, whereinR is CH₃ --(CH₂)_(n) --CH═CH--CH₂ --and n=8-10 or mixtures thereof.